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/* Copyright 2020 Frank Adams
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
// This software interfaces the Teensy 3.2 with a laptop pointing stick (aka trackpoint) that is not PS/2.
// Raw trackpoints use 4 resistive strain gauges for the left, right, up, and down detection.
// The connections from the Teensy are 3.3 volts, ground, x voltage to A0, and y voltage to A1.
// In the Arduino IDE, select Tools, Teensy 3.2. Also under Tools, select Keyboard+Mouse+Joystick
//
// Revision History
// Rev 1.0 - March 28, 2020 - Original Release
// Rev 2.0 - May 29, 2020 - Changed dead zone methodology
//
// declare and initialize variables
int x_read; // stores the reading from the X ADC
int y_read; // same for the Y ADC
char mx; // signed byte used by the Mouse.move function for x value. Positive value moves to the right
char my; // positive y value moves down
int x_delta; // signed 16 bit value gives x movement amount
int y_delta; // y version.
int x_center; //resting position of x sensor
int y_center; //resting position of y sensor
int noise_zone = 175; // dead zone around the center. Increase this number if
// the cursor moves without touching the TP. Decrease if
// too much force is needed to move the cursor.
void setup()
{
delay(1000); // delay a second to let things settle out
analogReadRes(13); // set ADC resolution to 13 bits (16 bit ADC but low 3 bits are random noise)
analogReadAveraging(8); // ADC will take the average of 8 reads
x_center = analogRead(A0); // store the center (no movement) position for x
y_center = analogRead(A1); // same for y.
// When the keyboard code is added, detect when Fn - F8 is pushed to indicate that
// x_center and y_center should be read again from the ADC. This would be because
// the operator notices the cursor is moving without being pushed.
}
//
// ************************************Main Loop***************************************************************
void loop() {
mx = 0; // for each loop, start with zero and update only if movement detected
my = 0; // same for y
//
x_read = analogRead(A0); // read the ADC tied to the X sensor
y_read = analogRead(A1); // read the ADC tied to the Y sensor
// Check if X or Y movement is beyond the dead zone
if ((x_read > (x_center + noise_zone)) || (x_read < (x_center - noise_zone)) || (y_read > (y_center + noise_zone)) || (y_read < (y_center - noise_zone))) {
// Only do the following if at least one reading is beyond the dead zone.
// Figure out if the X value is to the right or the left of the center resting value
if (x_read > x_center) { // is X ADC to the right of the resting position?
x_delta = (x_read - x_center) / 10; // find out how far beyond center. Divide by 10 to slow it down.
mx = byte(x_delta); // convert signed 16 bit to signed 8 bit
}
else { // X ADC is equal or to the left of the resting position
x_delta = ((x_center - x_read) / 10) * -1; // Answer should be negative so multiply by -1
mx = byte(x_delta); // convert signed 16 bit to signed 8 bit
}
// Figure out if the Y value is above or below the center resting value
if (y_read > y_center) { // is Y ADC above the resting position?
y_delta = ((y_read - y_center) / 10) * -1; // up movement is negative for Mouse.move function
my = byte(y_delta); // convert signed 16 bit to signed 8 bit
}
else { // Y ADC is equal or below the resting position
y_delta = ((y_center - y_read) / 10);
my = byte(y_delta); // convert signed 16 bit to signed 8 bit
}
}
// send the x and y data over usb if either one is not at center position
if ((mx != 0x00) || (my != 0x00)) {
Mouse.move(mx,my);
}
//
// **************************************End of trackpoint routine***********************************
//
delay(30); // wait 30ms before repeating next polling cycle
}